Set-square.



F. G. ALLEN.

SET SQUARE. APPLICATION FILED NOV. 30. 1914.

1,146,60& Patented July 13, 1915.

ATTORNEYS "ran STA" FRANK a. ALLEN, or BOULDER, COLdRADO.

SET-SQUARE.

masses.

Specification of Letters Patent.

Patented July :13, 1915.

Application filed November 30, 1914. Serial No. 874,811.

ToaZZ whom it may concern:

Be it known that I, FRANK G. ALLEN, a citizen of the United States, anda resident of Boulder, in the county of Boulder and State of Colorado,have made certain new and useful Improvements in Set-Squares, of whichthe following is a specification.

My invention is an improvement in drafting instruments, of the characteiparticularly described as set squares, and the invention has for itsobject to combine in a single instrument of the type in question anumber of scales or" measures, in such manner that when used inconnection'with a T-square, horizontal, vertical or inclined lines maybe drawn and measured at a single operation.

In the drawings: Figure 1 is a top plan' view of-the improved instrumentin use, and Fig. 2 is a similar view of another embodiment of theinvention.

The embodiment of the invention shown in Fig. l is, used in connectionwith a T- square consisting of a body 1 and a head 2 connected to thebody in the usual manner at one end thereof and at right angles to thebody. The instrument which may be constructed of any desired material,as for instance wood, metal, celluloid, paste board or the like,consists of three portions, namely a base 3, a side 4, at right anglesto the base, and a hypotenuse 5 connecting the remote ends of the baseand the side.

The base, side and hypotenuse are of equalwidth, and the triangularopening 6 at the center is preferably of as large area as may beconsistent with sufiicient strength and rigidity of the square-as awhole. The inner edges of the base, side and hypotenuse are parallelwith the outer edges, so that when for instance the base 3 is set withits outer edge against the T-square body, both the inner and outer edgesof the side 3 will be parallel with the edges of the body of theT-square. K

Each edge of the base, side and hypote nuse is provided with a scale,and the graduations of the scale may be of any desired unit ofmeasurement. It will be noted that the scale 7 on the outer edge of theside 4 is similar to the scale 8 on the inner edge of the base, whilethe scale 9 on the inner edge of the side 4: is similar to the scale 10on the outer edge of the base 3. That is, there are two sets each setconsistlng of two scales, and the two scales are at right angles to eachother. With this arrangement lines at right angles to each other will belaid ofi and measured at the same time. The scales 7 and 10 have theircommencement at the angle formed between the inner edges of the side andbase, scale 7 extending upward from its commencement or zero mark, andscale 10 extending. to the right from its commencement. .Othergraduations are, however, provided in connection with the scale 7,between the inner edge of the base and the outer edge, and in connectionwith scale 10 between the inner edge of the side and the outer edge. Theinner corners between the inner edges of the base, side and hypotenusemay be rounded by small arcs, as shown in Fig. 1, this being especiallydesirable to prevent cracking at the corners when the instrument is madeof celluloid. Scales 8 and 9 should have their commencement near theintersection of the base and side, but far enough from said intersectionto clear said rounded inner corner and to fall upon the straight part ofsaid inner edges, as shown in Fig. 1. By the particular arrangement ofscales, after a line has been drawn along the inner edge of the base,the zero mark of scale 7 may be brought to this line by merelyslidingthe set square to the right along the body of the T-square, withoutmoving the T-square. The set square will then be in position to measureand draw along the outer edge of the side 4 a line at rightangles to theline just drawn along the inner edge of the base, the scale 7 being inproper position to begin the measurement exactly from the line drawnalong the inner edge of the base.

The outer edge of the hypotenuse should be provided with a linear scale11 of the same unit of measurement as that of the scales 7 and 8, andthe zero mark or commencement should be in line with the inner edge ofthe base 3. When the improved square is made from celluloid or liketransparent material, the graduation marks should be on the under sideof the square, so as to read correctly when viewed through the body ofthe set square. Errors due to parallax are thus avoided. The inner edge.

of the hypotenuse is also provided with a 7 scale 12 of the same unit ofmeasurement as that of the scales 9 and 10.

If the instrument be made of metal or other opaque material, the sideedges of the base, side and hypotenuse may be beveled to avoid errorsdue to parallax. This arrangement'is shown in Fig. 2 wherein the setsquare consists of a base 13, a side 14 at right angles thereto, and ahypotenuse 15. The scales 16, 17, 18, 19, 20 and 21 corresponding inposition and .arrangement to the scales 7, 8, 9, 10, 11 and 12respectively, are arranged on beveled surfaces, eachbeveled surface atthe outer edges extending from near one angle to near the other. Aspace, however, is left at each angle of the instrument at the outeredge, as indicated at 22, not beveled, in order to prevent the setsquare from slipping too easily under the body of the T-square.. Theseplain surfaces 22 provide for ashoulder at each end of each side oftheset square for engaging the edge of the body of the T-square to hold theset square in position. At the inner edge of the side, base andhypotenuse the bevel may eX- tend the full length of the edge.

The invention consists in factof providing scales two or more, inconnection with the ondinary draftslnen in laying off lines, and thescales should be at one inner and one outer edge, and preferably atright angles to eachother, the commencement of the scale at the outeredge being in line with that inner edge at which a scale is providedwith the same units of measurement as those of the scale at said outeredge, the edges having the scales being parallel to the adjacent edges.

In use, the set square is used in connection with a T-square in theordinary manner, as shown in Fig. 1. \Vhen the square is placed with theouter edge of the'base 3 against the body 1 of the T-square, a line Imay be drawn and measured along the inner.

edge of the base 3; Then the zero mark of the scale 7 may be broughtupon this lines by sliding the set square to the right along form of setsquare used by scale 8, the scale 7 being in proper position.

to begin the measurement exactly from the line drawn along the scale 8.In order to extend the usefulness of the instrument, the linear scales9, l0 and 12 may have a different unit of measurement from the scales 7,8 and 11.

I claim:

A set square consisting of a base and a side at a rightangle" to eachother and a hypotenuse connecting the remote ends of the base and theside, the inner edges of the base, side and hypotenuse being parallel tothe outer edges of the base, side and hypotenuse respectively, the innerand outer edges of the base, side and hypotenuse having scales, the zeromarks of the scales atthe outeredge of the base and side being in linewith the inner edge of the side and base respectively, and the zero markof the scale at the outer edge of the hypotenuse being in line with theinner edge of the base, and each scale at an outer edge havingextensions in both directions from its zero mark, the zero marks of thescales at the inner edge of the base and the inner edge of the sidebeing near the intersection of said inner edges, 'and the zero mark ofthe scale at the inner edge of the hypotenuse beingnear the intersectionof the inner edge of the hypotenuse and the inner edge of the side.

FRANK G. ALLEN. WVitnesses:

- 'JNoJMOSSMArI,

J. E. DE KALB.

